In general, an automatic player piano is shifted between a recording mode of operation and a playback mode of operation. In the recording mode of operation, the keys are successively depressed by the fingers of a human player for specifying notes, and the pedals may be occasionally operated by the feet for prolonging the sounds, lessening the volumes or sustaining the notes. Since a lot of sensors are provided in association with the keys and the pedals, those key movements and pedal operations are detected to form pieces of the musical information which are memorized in a suitable storage. After formation of the pieces of the musical information, the automatic player piano is capable of shifting into the playback mode of operation. In the playback mode of operation, the pieces of the musical information are retrieved in succession from the storage for driving the keys and the pedals, if necessary, thereby allowing the automatic player piano to perform the music without the human player.
In an actual performance, each tone is loud or soft according to the strength of the key touch for an expressiveness, and, for this reason, the automatic player piano is provided with touch sensors for detecting the hammer velocities used for an estimation of the key touch. FIG. 1 shows a typical example of the automatic player piano provided with the touch sensors. In FIG. 1, reference numeral 1 designates a mechanical piano of the upright type which largely comprises a keyboard provided with a plurality of typically 88 keys, a key action mechanism provided in association with the keys for transmission of the key motions, a plurality of hammer assemblies respectively driven for rotations by the key action mechanism, a plurality of music wires struck with the hammer assemblies, respectively, and a plurality of damper assemblies respectively engageable with the music wires. Thus, the keys to the damper assemblies are incorporated in multiple, however, only one line of members, i.e., the key, the key action mechanism, the hammer assembly, the music wire and the damper assembly are illustrated in FIG. 1 and designated by reference numerals 2, 3, 4, 5 and 6, respectively. Though not shown in the drawings the mechanical piano 1 is further provided with a set of pedals. However, the mechanical piano of this type is well known in the art, so that no further description is incorporated.
The automatic player piano shown in FIG. 1 is accompanied with a controller 7 coupled at the input ports thereof to plural pairs of photo couplers and at the output ports thereof to a plurality of solenoid-operated actuators, and each pair of the photo couplers are spaced apart from each other along a traveling path of each hammer assembly, and optical paths of the photo couplers extend across the travel path, respectively. For the hammer assembly 4, the photo couplers 8 and 9 are located along the travel path thereof as will be seen from FIG. 1. By virtue of the multiple arrangement of the photo couplers 8 and 9, the motion of the hammer assembly 4 is detectable with the photo couplers, and the strength of the key touch is estimated on the basis of a time interval consumed between the interruptions of the optical paths of the photo couplers 8 and 9. In detail, if the human player depresses the key 2 with a large force, the large force is transmitted from the key 2 through the key action mechanism 3 to the hammer assembly 4, then allowing the hammer assembly 4 to rotate toward the music wire 5 at a large velocity. When the hammer assembly 4 is driven for rotation at the large velocity, the time interval is decreased in value, however, if the hammer rotates at a small velocity with a relatively small force, the time interval is prolonged. In general, the larger force the key 2 is subjected to, the shorter time interval the hammer assembly 4 consumes. Then, an inverse relationship is established between the force, or the key touch, and the velocity of the hammer assembly 4. In accordance with the inverse relationship, a piece of the key touch information is produced on the basis of the time interval calculated by the controller 7 and memorized therein.
The solenoid-operated actuators are provided in association with the keys and the pedals, respectively, and these solenoid-operated actuators are selectively energized by the controller 7 for actuations, thereby causing the keys and the pedals to be driven for selective movements, respectively. Then, if the piece of the key touch information is retrieved for the key 2 in the playback mode of operation, the solenoid-operated actuator 10 is energized with an electric power by the controller 7 to provide a power tantamount to that transmitted from the key 2 upon the original key depression. In this manner, the solenoid-operated actuators are selectively energized by the controller 7 to perform the music which was originally performed by the human player.
However, a problem is encountered in the prior-art automatic player piano in trammel of each photo coupler. As described hereinbefore, each hammer assembly is accompanied with a pair of photo couplers, so that the total number of the photo couplers is calculated as 88 multiplied by 2 or 176. These photo couplers should be precisely located at the respective positions, otherwise, the music produced in the playback mode of operation would be different from the original music. However, the precise trammel is not easy, because the hammers are different in size and in location depending upon the piano type, the model and the manufacturer and so on. In other words, the mechanical pianos have not been standardized yet. If each photo coupler is installed during the manufacturing process of the mechanical piano 1, the photo couplers may, make the manufacturing process to be a little bit complicated. However, the user occasionally requests the manufacturer to remodel the mechanical piano into an automatic player piano. This request provides a serious difficulty to the piano manufacturer, because the manufacturer hardly designs the photo couplers and the solenoid-operated actuators until the user's mechanical piano is checked by the manufacturer. After the user's mechanical piano is checked, the manufacturer can tailor the photo couplers and the actuators, so that a relatively long time period is consumed from the order for the remodeling to the completion of the work. This results in increasing of remodeling cost.
Moreover, the prior-art automatic player piano has another problem in stability of the production of the key touch information. This problem results from deformations of the component members which are usually made of wood, and a secular change in humidity due to heat attacks is causative of such a deformation. A large number of solenoid-operated actuators and the photo couplers are serious heat sources for the component members of wood. When the component members are deformed, the hammer velocity tends to be shifted, and, for this reason, the pieces of the key touch information do not indicate the original key touches during the service life of the automatic player piano.